A rigid tank is filled initially with 5.0 kg of air at a pressure of 0.5 MPa and a temperature of 500 K. The air is allowed to discharge
through a turbine into the atmosphere, developing work until the
pressure in the tank has fallen to the atmospheric level of 0.1 MPa.
Employing the ideal gas model for the air, determine the maximum
theoretical amount of work that could be developed, in kJ. Ignore
heat transfer with the atmosphere and changes in kinetic and potential
energy.

Ametal ring 4.20 cm in diameter is placed between the north and south poles of large magnets with the plane of its area perpendicular to the magnetic field. these magnets produce an initial uniform field of 1.12 t between them but are gradually pulled apart, causing this field to remain uniform but decrease steadily at 0.240 t/s . (a) what is the magnitude of the electric field induced in the ring? (b) in which direction (clockwise or counterclockwise) does the current flow as viewed by someone on the south pole of the magnet?